1. Field of the Invention
The present invention relates to a technical field of an imaging apparatus and a drive motor. More particularly, the invention relates to a technical field of reducing the number of components of the apparatus and achieving miniaturization thereof by simultaneously maintaining sufficient torque generated by a drive motor for moving movable members that constitute an iris or a shutter.
2. Description of Related Art
Some imaging apparatuses, such as a video camera and a still camera, are adapted to have a lens moving mechanism, which moves various kinds of lenses for focus control and for zooming in the direction of an optical axis, and also have an iris for adjusting an amount of light, and also adapted to move movable members (or diaphragm blades) constituting an iris in a plane perpendicular to an optical axis of an imaging optical system by utilizing a driving force of a drive motor thereby to open and close an optical path of an optical system and to adjust an amount of light (see, for example, the specification of Japanese Patent No. 3,295,415).
In this imaging apparatus, for instance, a turning arm for transmitting the driving force of the drive motor to the movable members is provided. A part of the turning arm is fixed to a shaft (or motor shaft) of the drive motor. An engaging section provided at an end part of the turning arm is slidably engaged with an engaging elongated hole formed in the movable member. A turning force of the turning arm is converted into a translational movement force for translational movement of the movable members to thereby move the movable members.
The drive motor described in the specification of Japanese Patent No. 3,295,415 is configured so that a magnet is disposed in a stator yoke. An output pin (that is, a member corresponding to the turning arm) provided in the magnet is outwardly protruded from a cutout formed in the stator yoke. Two pins formed of ferromagnetic materials in such a way as to be spaced from each other in the direction of rotation of the magnet are provided in the stator yoke. The output pin, which is turned as the magnet rotates, is held at each of movement ends in the direction of rotation thereof by being attached thereto by one of the two pins.